This invention relates to a system for monitoring compaction of material by a work implement, and more particularly to an information system for compaction machinery which measures compaction density on a first few passes to predict the number of compaction passes needed to meet specification.
As used in this patent specification the phrase xe2x80x9ccompaction machinexe2x80x9d and various approximations thereof refer to self-propelled mobile machines such as landfill, earth and asphalt compactors which are provided with a prime mover (for example an engine) on a carriage to drive rotating elements such as wheels or rollers serving as both carriage support and the compacting tool.
Despite the development of sophisticated and powerful compacting machinery it remains a time consuming and labor intensive chore to adequately compact material such as earth or asphalt at work sites such as construction sites, roads and the like. The material to be compacted is typically spread over the site in an uncompacted state and must be repeatedly traversed by a compaction machine until it is compressed to a desired degree of compaction. A common type of compacting machinery includes one or more heavy compacting wheels or rollers which compact the material in their path.
Compacting operations are still largely monitored and controlled by the machinery operators and supervisors on an intuitive basis, or by estimating results from laboratory information about the type of material being compacted. For example, a number of compaction passes required over a specific site material may be empirically determined or established by contract or local regulation. The number of passes is generally very conservatively selected to satisfy a range of environmental and material conditions, often resulting in unproductive passes over material already meeting the density specifications.
There have been several efforts to electronically provide the operator with detailed information regarding the real-time progress being made in the compaction operation. In U.S. Pat. No. 5,471,391, Gudat et al. disclose maintaining a detailed dynamic site model by precisely determining in three dimensional space the location of the compacting portions of the machine relative to the site. Information indicative of compaction, such as the number of passes a compacting wheel makes over a given area or elevational change from the uncompacted level, are automatically determined by continuously updating the site model.
Vibratory compactors typically utilize a drum having a mass eccentrically rotating at a rate near a resonance frequency of the compacted material to increase its density. In U.S. Pat. No. 5,177,415, Quibel et al. disclose continuously evaluating the degree of compaction of a material provided by vibrating compaction tool through calculation of the total applied static, dynamic and centrifugal forces.
In U.S. Pat. No. 4,979,197, Troxler, Sr. et al. disclose a device mounted to a compaction machine in a spaced apart relation from the surface to emit nuclear radiation and counting photons back scattered from the material. An ultrasonic transducer or laser measuring the air gap purportedly permits accurate compensation therefor in a density determination. The machine is equipped with a pair of signal lights to indicate whether or not a desired degree of compaction has been reached.
Although each of the foregoing are individually intended to provide an operator with information to improve compaction efficiency, there continues to be a need to increase the safety and reliability of the compaction measurement, and in some cases provide additional information useful for compaction of the material.
The present invention is directed to overcoming one or more of the disadvantages set forth above.
Compaction performance follows a well behaved response curve for a particular material condition/compaction machine combination. According to one aspect of the present invention, compaction performance is predicted using a compaction response curve determined from measured values values representative of material density after a first and second pass by a compaction machine. The response curve is used to predict the number of passes required by the compaction machine to reach a desired density for the material.
Other details, objects and advantages of the invention will become apparent as certain present embodiments thereof and certain present preferred methods of practicing the same proceeds.